Microbial risks during indoor leafy green production: Current knowledge and future research needs

Food crop production in controlled environments is an increasingly important sector of U.S. and global agriculture. According to the 2019 Census of Horticultural Specialties, sales from “food crops grown under protection” were roughly $700 million in the U.S. These crops include primarily tomatoes, lettuce, cucumbers, peppers, berries, and herbs and account for 54% of the total production (cwt) in the U.S. Controlled environment agriculture (CEA) takes advantage of technologies and automation to modify production climates, shield crops from biotic and abiotic stresses, and optimize environmental factors that maximize plant yield and quality. Greenhouses and indoor warehouses or shipping containers are common CEA structures, and hydroponics, soilless substrate culture, and vertical farming systems are common CEA growing systems. Although CEA helps exclude pests and diseases from produce, pathogen issues can still occur in these operations. Foodborne pathogens enter CEA similar to field-grown crops via: (i) contaminated water, (ii) unsanitary equipment, (iii) contaminated incoming materials such as seeds or plant materials, (iv) employees and staff, and (v) insects and animals. To address this need, we will identify both best practices and research gaps in the peer-reviewed literature, technical abstracts, and grey literature. Semi-structured interviews will also be conducted with CEA operators producing leafy greens across the U.S. to gather information about current practices and potential food safety gaps. Academic researchers and regulatory experts in food safety will also be consulted. The result will be a final synthesis of the available knowledge to provide key takeaways, evidence-based practices, and knowledge gaps on microbial risks during indoor leafy green production.